Electron beam convergence apparatus



Dec. 29, 1964 e. w. SINGLEBACK ELECTRON BEAM CONVERGENCE APPARATUS Filed Aug. 24. 1960 INV EN TOR. Georaell-LSiIBlebacK BY QQX $3 v QEQQNQQ ornell United States Patent 3,163,797 ELEQTRQN BEAM QUNVERGENE APPARATUS George W. Singlehacir, Pennsauiren, Nnlfi, assignor to Radio tlorporation of America, a corporation of Delaware Filed Aug. 24, 1969, Ser. No. 51,747 12 Claims. ((Ii. 315-22) This invention relates to color television receivers, and particularly to means for making the three electron beams of a color kinescope converge at all scanned points on the kinescope screen.

Color kinescopes of the shadow mask type normally include three electron guns positioned in the neck of the kinescope and a target electrode including an aperturcd shadow mask between the electron guns and a luminescent screen of phosphor dots arranged in groups of three in registry with respective apertures of the mask. Static means are provided for making the three electron beams converge and pass through the same aperture at the center of the shadow mask plate. The three beams, after passing through the shadow mask, respectively strike three phosphor dots, each emitting light of a diiferent color. All three beams are deflected by a common horizontal and vertical deflection system so that the beams, systematically scan the kinescope target. The more the three beams are deflected from the center of the target, the greater may be the misconvergence of the beams when they reach the shadow mask. It is, therefore, customary to provide dynamic electromagnetic means for correcting the misconvergence of the beams as a function of the angular deflection of the beams from the center of the kinescope target. For this purpose, current waveforms of generally parabolic shape are derived from the horizontal and vertical deflection circuits and are employed, in conjunction with three convergence electromagnets, to dynamically converge the three beams so that they pass through the same aperture in the shadow mask at all points of the entire scanned area of the kinescope target. 1

Careful adjustment of the dynamic convergence circuits is needed so that each convergence electromagnet is energized by a current having such amplitude and wave shape as to effect the desired beam convergence at all points on the kinescope target electrode. In some prior art arrangements, after beam convergence has been achieved initially in one area of the kinescope screen, there has been such interaction between controls that the adjustment of the convergence circuit controls in order to achieve convergence in another area of the kinescope screen has been found to so affect the initial beam convergence as to cause considerable misconvergence of the beams in the first screen area. Consequently, a readjustment to achieve beam convergence in the first screen ice nected in series with the anode-to-cathode circuit of the vertical deflection output tube to supply energy to the elect-romagnet windings at vertical deflection frequency. Arrangements of this character are disclosed in Patent No. 2,903,622, issued September 8, 1949, to I. C. Schopp. in such systems, the substantially parabolic current waves at horizontal deflection frequency are obtained by the conversion of pulse type energy derived from the horizontal deflection output circuits. Also, the substantially parabolic current waves at vertical deflection frequency are derived from the substantially sawtooth currents flowing in the anode-to-cathode circuit of the vertical deflection output tube.

It is an object of this invention to provide improved and less costly than previously used circuit arrangements by which to more readily effect the convergence of the three electron beams of a tricolor kinescope. 7

Another object of the invention is to provide an improved and less costly circuit arrangement-for producing a desired proportionality between the alternating current and direct current components of a substantially parabolic convergence wave at the vertical deflection frequency for energizing the beam convergence electromagnets.

Still another object of the invention is to provide a system for developing a substantially parabolic current Wave with a sawtooth component at horizontal'deflection frequency for energizing the beam convergence electromagnets and utilizing a single winding on the horizontal deflection output transformer.

in accordance with one aspect of the invention, the proper ratio between alternating current and direct cur rent components of the parabolic current wave for energizing the beam convergence electromagnets at vertical deflection is achieved by a capacitive and resistance network means connected between the cathode circuit of the vertical deflection output tube and the vertical deflection frequency windings of the convergence electromagnets. u The resistive component of such a network and a self-biasing resistor connected to the vertical deflection output tube cathode are so proportioned to one another as to effect the desired biasing of the vertical deflection output tube and, at the same time, to effect the desired proportioning of the alternating current and direct current components of the convergence current wave.

In accordance with another aspect of the invention, a

single winding placed on the horizontal deflection output I transformer is connected to two coils having variable inductance means by which to control the substantially parabolic current waves through the beam convergence electromagnets at the horizontal deflection frequency. One of these coils is conductively connectedto two of the beam convergence electromagnets for supplying the substantially parabolic current waves to these electro magnets. The other coil is inductively coupled'to the same two electromagnets for supplying thereto the saw-. tooth current component of the convergence wave. The other of said coils is additionally conductively connected to the third beam convergence electromagnet for supplypeak amplitudes of the waves and their particular shapes.

In certain prior art systems, this control of the energizing current waves is achieved by diodes connected in the circuit supplying energy to the electromagnet windings at horizontal deflection frequency and by means of a parallel arrangement of resistance and inductance coning both the parabolic current wave and the sawtooth component to the third electromagnet.

For albetter understanding of the invention together with additional objects, features and advantages thereof, reference will which:

PEGURE 1 is a fragmentary sectional view of the neck portion of a shadow mack typecolor kinescope showing the relationship of the convergence electroniagnets and the electron beams respectively controlled thereby; and,

FIGURE 2 is a schematic circuit diagram vof apparatus embodying the invention and by which the-beam convergence electromagnets of a shadow mask type color be made to the accompanying drawing in,

kinescope are energized and controlled at the horizontal and vertical deflection frequencies.

Reference first is made to FIGURE 1 for a description of the physical relationship of the convergence electromagnets and the electron beams controlled respectively thereby as presently embodied in commercial color television receivers. This figure is a transverse sectional view of the neck portion of a color kinescope as it appears when viewed from the luminescent screen end of the kinescope. The three electron beams 6 are located respectively between pairs of pole pieces 7, 8 and 9 located internally of the neck 10 of the kinescope and extending inwardly from the ends of the substantially U-shaped cores of green, red and blue convergence electromagnets 11, 12 and 13 respectively mounted externally around the neck 10 of the kinescope. Each of the convergence electromagnets is provided with a horizontal deflection frequency winding and with a vertical deflection frequency winding. The horizontal deflection frequency windings are designated 14G, 14R and 143 respectively for the green, red and blue electromagnets 11, 12 and 13. The vertical deflection frequency windings are designated 15G, 15R and 15? respectively for the green, red and blue electromagnets 11, 12 and i3. Energization of the electromagnet windings produces a magnetic field between the corresponding pole pieces which moves the corresponding electron beam radially in the direction of the arrows associated with the beams 6. There also may be included as part of the convergence electromagnetic structure some means for elfecting a static convergence of the electron beams 6. The static convergence means may be permanent magnets associated with the respective convergence electromagnets or may comprise windings on the respective electromagnets for energization by direct current of the proper amplitude and polarity to effect the desired static convergence of the electron beams. Such static convergence means is known'and, since it forms no part of the present invention and is not needed for an understanding of this invention, it is not shown.

FIGURE 2 discloses schematically the circuits for developing and applying to the convergence electromagnets currents of proper waveform to effect dynamic convergence of the three beams of a tricolor kinescope. It is to be understood that a color television receiver in which the present invention may be embodied includes all of the necessary apparatus for receiving a composite color television signal conforming to the present standards esstablished by the Federal Communications Commission and for processing such signal for impression upon a three-beam color kinescope serving as an image reproducing device, such as a shadow mask color kinescope of the RCA type 21CYP22 or 21CYP22A. The three convergence electromagnets and the energizing windings thereof are designated by the same reference characters as used in FIGURE 1.

The horizontal deflection frequency windings of the beam convergence electromagnets are energized by substantially parabolic current waves which are derived from the horizontal deflection circuit 16. This circuit includes a deflection output tube 17 and an output transformer 18, and is connected in a known manner to the horizontal deflection yoke and to the high voltage rectifier circuits as indicated. The output transformer is also provided with a secondary Winding 19 in which voltage pulses at the horizontal deflection repetition rate are produced. These pulses are impressed upon red-green parabola amplitude control coil 21 and blue parabola amplitude control coil 22, the respective inductances of which may be varied as indicated by means such as ferrite cores movable within the coils in a known manner. The coil 21 is connected to an intermediate point of another variable inductance red-green parabola differential control coil 23, the terminals of which are connected to corresponding terminals of the green and red horizontal frequency windings MG and MR respectively of the green and red convergence electromagnets 11 and 12. The other two corresponding terminals of the windings MG and MR are connected to the terminals of a red-green sawtooth current coil 24 which is inductively coupled to the coil 22 to provide the sawtooth current component for the windings 14G and MR and which has an intermediate point connected to ground, thereby providing a return path for the parabolic currents through the electromagnet windings. The coil 22 is connected to one terminal of the winding 14B of the blue convergence electromagnet t3, the other terminal of this winding being grounded. The relationship of the inductively coupled coils 22 and 2 is such that a variation of the inductance of the coil 22 by its movable ferrite core has little, if any, significant effect upon the coil 24.

A red-green sawtooth differential control potentiometer 25 is coupled across the coil 23 and has a movable contact which is connected to the movable contact of a red-green sawtooth amplitude control potentiometer 26 connected to the grounded junction point of a series circuit including resistors 27 and 28 and associated diodes 29 and 31, the series circuit being connected across the coil 23. A blue sawtooth amplitude control potentiometer 32 serving as a variable resistance is coupled across the winding MB of the blue convergence electromagnet 13. Also connected across this winding is a series circuit of a resistor 3-3 and a diode 34.

The operation and control of the horizontal frequency windings 146, MR and 14B of the green, red and blue convergence electromagnets ll, 12 and 13 respectively is essentially the same as that disclosed in Schopp Patent No. 2,903,622 previously referred to. For completeness of the present disclosure, however, such operation will be briefly described hereinafter.

The vertical frequency windingsiSG, 15R and 15B of the green, red and blue convergence electromagnets 11, 12 and 13 respectively, are energized by substantially parabolic current waves which are derived from the vertical deflection circuit 35. This circuit includes an output tube 36 and a transformer 37 the primary winding 38 of which is connected in the output circuit of the tube 36. A secondary winding 35? of this transformer is connected in a known manner to the vertical deflection yoke as indicated. Two other secondary windings 41 and 42 are provided on the transformer 37 for the development of voltage pulses at the vertical deflection frequency for use in energizing the vertical frequency windings of the convergence electromagnets.

The cathode of the vertical deflection output tube 36 is connected to a self-biasing network including a resistor 43 and a shunt-connected capacitor 44. Also connected to the cathode of this tube is a network 4.5 which functions to properly proportion the alternating current and direct current components of the substantially parabolic current Waves which traverse the vertical frequency windings 15G, 15R and 15B of the convergence electromagnets. This network consists of a resistor 46 and a capacitor 47 connected in shunt therewith. The function ing of this network to achieve the desired result will be described hereinafter. Potentiometers 48 and 49 connected in se ies between the proportioning network and ground serve to control the convergence currents flowing in the vertical frequency windings of the convergence electromagnets. The red-green parabola amplitude control potentiometer 4-3 simultaneously controls the current for the green and red vertical frequency windings 15G and 15R and the blue parabola amplitude control potentiometer 49 independently controls the current in the blue electromagnet winding 153.

A red-green sawtooth amplitude control potentiometer 51 having its resistive element connected across the secondary transformer winding 41 and its movable contact connected to the series circuit arrangement of the green and red vertical frequency convergence windings 156 and 158. serves to control the amplitude of a substantially sawtooth current wave applied to these windings for combination with the substantially parobolic current wave in the usual manner to tilt or phase (i.e., shape) the parabolic currents flowing in these windings. A redgreen parabola differential control potentiometer 52, having its resistive element connected in parallel with the series arrangement of the green and red electromagnet windings 15G and 15R and its movable contact con nected through the movable contact and resistive element of a red-green sawtooth differential control potentiometer 53 and through the transformer secondary winding 42 to the junction point between the windings 15G and 15R, functions to vary the distribution of the parabolic current in the windings ISO and ER. A blue sawtooth amplitude control potentiometer 54, having its resistive element connected across the transformer secondary winding ll and its movable contact connected to the blue vertical frequency electromagnet winding 15B, functions generally to control the amplitude and polarity of a substantially sawtooth current flowing in the blue convergence winding for combination with the substantially parabolic current wave to tilt or phase (i.e., shape) the parabolic wave in this winding in the usufl manner. The adjustment of the movable contact of the red-green sawtooth differential control potentiometer 53 controls the distribution of the sawtooth current in the green and red electromagnet windings lSG and 15R.

In general, the circuits of FIGURE 2 function to vary the currents through the windings of the convergence elcctromagnets ll, 12 and 13 substantially as a parabolic function with respect to both the horizontal and vertical beam deflections for raster scanning. The energization of the electromagnet windings MG, MK and 1 53 at the horizontal deflection frequency is accomplished by the conversion of the voltage pulses developed in the winding 19 of the horizontal deflection transformer 1% into the parabolic current waves applied to these electromagnet windings. This conversion is accomplished in two main steps. The convergence electromagnet circuits appear essentially inductive to the voltage pulses developed in the transformer winding 19. Hence, the pulses are eifectively integrated to form generally sawtooth waves which traverse the coils 21 and 22. A second integration of these sawtooth waves is effected by the convergence control circuits to produw the desired substantially parabolic current waves for traversal of the electromagnet windings. Since the parabolic current waves are produced by the integration of the sawtooth waves, the parabolas are not symmetrical but are tilted so that the troughs of the parabolas do not occur at the centers of the respective waves. This is due to the fact that the sawtooth wave from which the parabolic wave is derived has its peak toward one end of the wave. In order to shape the parabolic wave more symmetrically so that its trough does occur substantially midway between its peaks, a sawtooth current component is combined with the parabolic wave component. This additional sawtooth current for tilting the parabolic current traversing the green and red electromagnet windings MG and MR is derived from the winding 24- which, by virtue of its coupling to the coil 22, has induced therein voltage pulses at the horizontal deflection frequency. These voltage pulses are integrated by the essentially inductive circuits connected to the winding 24 into substantially sawtooth current waves.

The energization of the electromagnet windings 15G, 15R and 153 at the vertical deflection frequency is accomplished by the conversion of a portion of the suhstantially sawtooth current flowing in the cathode circuit of the vertical deflection output tube 36 into substantially parabolic current waves applied to these electromagnet windings. This sawtooth current is effectively integrated into a parabolic current wave by the convergence electro magnet circuits which appear essentially inductive at the vertical deflection frequency. Also, the voltage pulses namic convergence controls, the beams should be stati-v cally converged at the center of the screen by any known means, such as referred to previously in the description of FIGURE 1.

In the horizontal deflection frequency convergence control circuits, the parabola current control coils 21, 22 and 23 are most effective in controlling beam convergence at the right side of the luminescent screen and the sawtooth current control potentiometers 25, 26 and 32 are most eflective in controlling beam convergence at the left side of the screen. The parabola current amplitude con- 7 trol coil 21 and the sawtooth current amplitude control potentiometer 2s respectively control the parabolic and sawtooth currents similarly in the green and red electromagnet windings MG and MR so as to move the green and red beams radially in the same sense with the respect to the longitudinal axis of the kinescope and by the same amount. The parabola current differential control coil 23 and the sawtooth current differential control potentiometer 25 respectively control the parabolic and sawtooth currents in the green and red electromagnet windings MG and MR so asto increase the current in one winding and to decrease it by a like amount in the other winding, thereby moving the green and red beams radially in opposite senses with respect to the longitudinal axis of the kinescope and by the same amount. By proper adjustments of the control coils 21 and 23 and potentiometers 25 and as the red and green beams may be converged dynamically at horizontal deflection frequency over the entire screen of the kinescope. Theblue beam is brought into dynamic convergence with the red and green beams at horizontal deflection frequency by independent adjustments of the control coil 22 and the potentiometer 32.

In the vertical deflection frequency control circuits, the parabola current control potentiometers 48, 49 and 52 are most effective in cont-rolling beam convergence in the lower portion of the luminescent screen and the sawtooth current control potentiometers 51, 53 and 54- are most effective in controlling beam convergence in the. upper portion of the screen. The parabola amplitude control potentiometer 43 and the sawtooth amplitude control potentiometer Sl respectively control the parabolic and sawtooth currents similarly in the green and red electromags net windings MG and HR so as to move the green and red beams radially in thesame sense with respect to the longitudinal axis of the kinescope and by thesame amount. The parabola differential control potentiometer 52 and the sawtooth differential control potentiometer 5?: respectively control the parbolic and sawtooth currents in the green and red electromagnet windings 156 and 15R so as to increase the current in one winding and to decrease it by a like amount in the other winding, thereby moving the green and red beams radially in opposite senses with respect to the longitudinal axis of the kinescope'and by the same amount.

ometers 48, 51, 52 and 53, the green and red beams may By proper adjustments of the potentithe aid of special test apparatus such as an RCA NR-61A color bar generator adjusted to display a cross-hatch of spaced vertical and horizontal bars on the luminescent screen on the color kinescope. Each bar of such a pattern consists of green, red and blue lines. When the three beams are properly converged both statically and dynamically in all areas of the screen, all bars of the pattern are white. When the beams are not properly converged, the colored lines constituting components of the bars are discernible and appear in spaced relation to one another.

The adjustment of the dynamic beam convergence circuits of FIGURE 2 may be made by observing the following sequence of operations, after first having achieved static convergence of the three electron beams at the center of the luminescent screen by suitable adjustment of the static convergence means, such as the permanent magnets previously referred to in connection with the descrip tion of FIGURE 1. Preferably, the vertical deflection frequency convergence circuit adjustments should be made first in the following order with a cross-hatch pattern of vertical and horizontal bars displayed on the luminescent screen:

(1) Adjust potentiometer 48 to superimpose the green and red vertical lines at the bottom of the center vertical bar.

(2) Adjust potentiometer 51 to super-impose the green and red vertical lines at the top of the center vertical bar.

(3) Alternate steps 1 and 2, if necessary, to achieve equal convergence of the green and red vertical lines of the center vertical bar from top to bottom of the screen.

(4) Adjust potentiometer 52 to superimpose the green and red horizontal lines of the lower horizontal bar.

(5) Adjust potentiometer 53 to superimpose the green and red horizontal lines of the upper horizontal bar.

(6) Alternate steps 4 and 5, if necessary, to achieve equal convergence of all green and red horizontal lines of the bar pattern from top to bottom of the screen.

7. Adjust potentiometers 49 and S4 to converge the blue horizontal lines of the bar pattern with the superimposed green and red horizontal lines.

Having suitably achieved dynamic convergence of the beams at vertical deflection frequency, the control devices of the circuits for eflecting dynamic beam convergence at horizontal deflection frequency should then be made in the following order with the same cross-hatch pattern displayed on the screen:

(1) Adjust coil 22 to make straight the blue horizontal line at the right center of the screen.

(2) Adjust potentiometer 32 to make straight the blue horizontal line at the left center of the screen.

(3) Adjust coil 21 to superimpose the green and red vertical lines of the vertical bars at the right side of the screen.

(4) Adjust coil .23 to superimpose the green and red horizontal lines of the horizontal bars at the right side of the screen.

(5) Readjust coil 22, if necessary, to superimpose the blue horizontal line at the right center of the screen with the converged red and green horizontal lines or" the center horizontal bar.

(6) Adjust potentiometer 26 to superimpose the green and red vertical lines of the vertical bars at the left side of the screen.

(7) Adjust potentiometer 25 to superimpose the green and red horizontal lines of the horizontal bars at the left side of the screen.

In order to decrease the interaction between the various convergence controls, it is necessary to make the magnitude of the D.C. component of the convergence current waves track (i.e. change correspondingly) with peak-topeak amplitude changes of the AC. component of these waves. The D.C. component should have a magnitude suitable to correct any error made in the static convergence of the beams made by the application of the AC. component of the substantially parabolic dynamic convergence current to the electromagnet windings. The tracking of the D.C. and A.C. components of the convergence current waves is efiected by suitably proportioning these two components as they are applied to the electromagnet windings.

In the convergence circuits operating at horizontal deflection frequency, this proportioning is elfected by means of the circuits including resistors 27, 28 and 33 and rectifiers 29, 31 and 34 as disclosed in the previously mentioned Schopp Patent No. 2,903,622.

In the convergence circuits operating at vertical deflection frequency, the proportioning of these components is effected by the resistive-capacitive proportioning network 45. Both the D.C. and AC. components of the convergence wave are derived from a portion of the sawtooth current conducted by the vertical output tube 36, the remaining portion of the tube current being passed through its associated cathode biasing circuit including resistor 43 and capacitor 44. The D.C. component of the convergence wave is applied to the electromagnet windings 15G, 15R and 153 through the resistor 46 while the AC. component is applied to these windings through the capacitor 47. By suitably choosing the values of the resistors 43 and 46 and of the capacitors 44 and 47, the desired proportionality of the D.C. and AC. components of the convergence wave may be achieved and, at the same time, a suitable bias for the tube 36 may be developed for proper operation of the vertical deflection output circuit.

The values of these circuit elements, in any particular embodiment, depends upon the other circuit elements used including the control potentiometers, the electromagnet windings, the type of vertical deflection output tube, etc. In general, the D.C. component of the sawtooth current through the tube 36 is greater in proportion to the AC. component of this current than is desired for proper operation of the beam convergence circuits. This also is true of the parabolic current into which the sawtooth current is converted and which is applied to the convergence electromagnet windings 15G, 15R and 1513. What is required of the circuits including resistors 43 and 46 and capacitors 44 and 47 is to conduct through the biasing circuits including resistor 43 and capacitor 44 a sawtooth current with a D.C.-to-A.C. component ratio which is sufliciently greater than the D.C.-to-A.C. ratio of the total sawtooth current through the tube 36 so that the D.C.-to-A.C. component ratio of the sawtooth current through the network 45 is decreased sufliciently to result in the production of a parabolic current wave for the convergence circuits having such a D.C.-to-A.C. component ratio that, at the troughs of the parabolic wave, the currents through the convergence electromagnet windings always have the same magnitude relative to a reference point, irrespective of the particular shape and peak-to-peak amplitude of the Wave as determined by the adjustments of the control potentiometers 48, 49, 51, 52, 53 and 54. Thus, any interaction between these various controls is minimized, thereby greatly facilitating the achievement of dynamic convergence of the electron beams.

What is claimed is:

1. In a color television receiver including a color kinescope having a screen luminescing in difierent colors when impinged by a plurality of electron beams adapted to be deflected together over said screen in successive trace scansion periods and alternating retrace scansion periods, a beam convergence system comprising: a plurality of beam convergence electromagnets having coils which effeet the convergence of said beams when energized by respective parabolic current waves each having crests occurring during beam retrace scansion periods and troughs occurring substantially at the middle of beam trace scansion periods, and each having direct current and alternating current components related to one another in a predetermined ratio such that, at the troughs of said parabolic current waves, the respective parabolic Waves always have the same magnitudes irrespective of the particular shapes and peak-to-peak amplitudes of said parabolic waves; a beam deflection system traversed by a sawtooth current wave for effecting said beam scansions over said screen, said sawtooth current wave having direct current and alternating current components related to one another in a ratio greater than said predetermined parabolic current wave ratio; two current dividing circuits including respective impedance means and connected to said deflection system for traversal by respective portions of said sawtooth current wave, the impedance means of one of said circuits comprising a resistor-capacitor network, said respective impedance means having such values as to enable proper operation of said beam deflection system and being proportioned relative to one another such that the sawtooth current wave traversing said one current dividing circuit has said predetermined ratio of direct current and alternating current components; and means connecting said one current dividing circuit to said electromagnet coils to cause the traversal of said coils by respective parabolic current waves having said predetermined ratio of direct current and alternating current components, whereby said beam convergence system can be adjusted to provide dynamic beam convergence at the edges of the tinescope screen without materially changing the beam convergence at the center of the screen.

2. In a color television receiver including a color kinescope having a screen luminescing in different colors when impinged by a plurality of electron beams adapted to be deflected together over said screen in successive trace scansion periods and alternating retrace scansion periods, a. beam convergence system comprising: a plurality of beam convergence electromagnets having coils which effect the convergence of said beams when energized by respective parabolic current waves each having crests occurring during beam retrace scansion periods and troughs occurring substantially at the middle of beam trace scansion periods, and each having direct current and alternating current components related to one another in a predetermined ratio such that, at the troughs of said paraboiic current waves, the respective parabolic waves always have the same magnitudes irrespective of the particular shapes and peak-to-peak amplitudes of said parabolic waves; a beam deflection system traversed by a sawtooth current wave for eifecting said beam scansions over said screen, said sawtooth current wave having direct current and alternating current components related to one another in a ratio greater than said predetermined parabolic current wave ratio; two resistor-capacitor network means connected to said deflection system for traversal by respective portions of said sawtooth current wave, said two network means having such resistance and capacitance values as to enable proper operation of said beam deflection system and being proportioned relative to one another such that the sawtooth current wave traversing one of said network means has said predetermined ratio of direct current and alternating current components; and means connecting said one resistor-capacitor network means to said electromagnet coils to cause the traversal of said coils by respective parabolic current waves having said predetermined ratio of direct current and alternating current components, whereby said beam convergence system can be adjusted to provide dynamic beam convergence at the edges of the kinescope screen without materially changing the beam convergence at the center of the screen.

3. In a color television receiver including a color kinescope having a screen luminescing in different colors when impinged by a plurality of electron beams adapted to be deflected together over said screen in successive trace scansion periods and alternating retrace scansion periods, a beam convergence system comprising: a plurality of earn convergence electromagnets having coils which effeet the convergence of said beams when energized'by respective parabolic current waves each having crests occurring during beam retrace scansion periods and troughs occurring substantially at the middle of beam trace scanwaves; a beam deflection system traversed by a sawtooth current wave for effecting said beam scansions over said screen, said sawtooth current wave having direct current and alternating current components related to one another in a ratio greater than said predetermined parabolic current wave ratio; two resistor-capacitor network means connected to said deflection system for traversal by respective portions of said sawtooth current wave, said two network means having such resistance and capacitance values as to enable proper operation of said beam deflection system and being proportioned relative to one another such that the sawtooth current wave traversing one'of said network means has said predetermined ratio of direct current and alternating current components; potentiometer means having at least a resistive element connected in series with said one resistor-capacitor network means for traversal by said sawtoothcurrent wave traversing said one resistorcapacitor network means; and means connecting said potentiometer means to said electromagnet coils to cause the traversal of said coils by respective parabolic current waves having said predetermined ratio of direct current and alternating current components, whereby said beam convergence system including said potentiometer means can be adjusted to provide dynamic beam convergence at the edges of the kinescope screen without materially changing the beam convergence at the center of the screen.

4. in a color television receiver including a color linescope having a screen luminescing in different colors when impinged by a plurality of electron beams adapted to be deflected together over said screen in successive L ace scansion periods and alternatingretrace scansions periods, a beam convergence system comprising: a plurality of beam convergence electromagnets having coils which effect the convergence of said beams when energized by respective parabolic current waves each having crests occurring during beam retrace scans-ion periods and troughs occurring substantially at the middle of beam trace scansion periods, and each having direct current and alternating current components related to one another in a predetermined ratio such that, at the troughs of said parabolic current waves, the respective parabolic waves always have the same magnitudes irrespective or" the particular shapes and peak-to-peak amplitudes of said parabolic waves; a beam deflection system traversed by a sawtooth current wave for effecting said beam scansions over said screen, said sawtooth current wave having direct current and alternating current components related to one another in a ratio greater than said predetermined parabloic current wave ratio; two resistor-capacitor network means connected to said deflection system for traversal by respective portions or" said sawtooth current wave, said two network means having such resistance and capacitance values as to enable proper operation of said beam deflection system and being proportioned relative to one another such that the sawtooth current wave traversing one of said network means has said predetermined ratio of direct current and alternating current components and such that the sawtooth current wave traversing the other of said network means has a greater ratio of direct current and alterna-tmg current components; two potentiometers having their respective resistive elements connected in series with magnet coil by a parabolic current wave having said predetermined ratio of direct current and alternating current components; and means connecting the other of said potentiometers to a second one of said electromagnet coils to cause the traversal of said second electromagnet coil by a parabolic current wave having said predetermined ratio of direct current to alternating current components, whereby said beam convergence system including said two potentiometers can be adjusted to provide dynamic beam convergence at the edges of the kinescope screen without materially changing the beam convergence at the center of the screen.

5. In a color television receiver including a three-beam color kinescope having a screen lurninescing in different colors when impinged by electron beams and provided with a field frequency deflection system for said beams, a beam convergence system comprising: three beam convergence electromagnets having respective energizing coils; convergence waveforms generating circuits coupled from said deflection system to said electromagnet coils to provide current waves in said coils having direct current and alternating current components and generally parabolic waveshapes with crests occurring during the blanking intervals between successive field scansions and troughs occurring at the middle of each of said field scansions; and resistor-capacitor proportioning network means connected in circuit with said convergence Waveform generating circuits to divert sufficient current from said deflection system to suitably energize said electromagnet coils without detracting from the proper operation of said deflection system, said network means being proportioned to so relate the direct current and alternating current components of the parabolic current waves that, at the troughs of said waves, the respective currents through said electromagnet coils always have substantially the same magnitudes irrespective of the particular shapes and peak-topeak amplitudes of said waves, whereby said convergence waveform generating circuits can be adjusted to provide dynamic beam convergence at the edges of the kinescope screen without materially changing the beam convergence at the center of the screen.

6. In a color television receiver including a three-beam color kinescope having a screen luminescing in different colors when impinged by electron beams and provided with a field frequency deflection system for said beams, a beam convergence system comprising: three beam convergence electromagnets having respective energizing coils; convergence waveform generating circuits coupled from said deflection system to said electromagnet coils to provide current waves in said coils having direct current and alternating curent components and generally parabolic waveshapes with crests occurring during the blanking intervals between successive field scansions and troughs occurring at the middle of each of said field scansions; and proportioning network means including a parallel arrangement of a resistor and a capacitor connected in circuit with said convergence Waveform generating circuits to divert sufficient current from said deflection system to suitably energize said electromagnet coils without detracting from the proper operation of said deflection system, said resistor and capacitor being proportioned to so re late the direct current and alternating current components of the parabolic current waves that, at the troughs of said waves, the respective currents through said electromagnet coils always have substantially the same magnitudes irrespective of the particular shapes and peak-to-peak amplitudes of said waves, whereby said convergence waveform generating circuits can be adjusted to provide dynamic beam convergence at the edges of the kinescope screen without materially changing the beam convergence at the center of the screen.

7. In a color television receiver including a three-beam color kinescope having a screen lurninescing in different colors when impinged by electron beams and provided with a field frequency deflection system for said beams, a beam convergence system comprising: an electron tube conducting a substantially sawtooth current connected in said deflection system; three beam convergence electromagnets having respective energizing coils; convergence waveform generating circuits coupled from said deflection system to said electromagnet coils to provide current Waves in said coils having direct current and alternating current components and generally parabolic waveshapes with crests occurring during the blanking intervals between successive field scansions and troughs occurring at the middle of each of said field scansions; and proportioning network means including a parallel arrangement of a resistor and a capacitor connected in series between said electron tube and said convergence waveform generating circuits to divert sufficient current from said deflection system to suitably energize said electromagnet coils and to contribute to such biasing of said electron tube as to insure proper operation of said deflection system, said resistor and capacitor being proportioned to so relate the direct current and alternating current components of the parabolic current waves that, at the troughs of said waves, the respective currents through said electromagnet coils always have substantially the same magnitudes irrespective of the particular shapes and peak-to-peak amplitudes of said waves, whereby said convergence waveform generating circuits can be adjusted to provide dynamic beam convergence at the edges of the kinescope screen without materially changing the beam convergence at the center of the screen.

8. In a color television receiver including a three-beam color kinescope having a screen lurninescing in different colors when impinged by electron beams and provided with a field frequency deflection system for said beams, a beam convergence system comprising: an output electron tube connected in said deflection system and having a cathode circuit including a resistor-capacitor biasing network; three beam convergence electromagnets having respective energizing coils; convergence waveform generating circuits coupled from said deflection system to said electromagnet coils to provide current waves in said coils having direct current and alternating current components and generally parabolic waveshapes with crests occurring during the blanking intervals between successive field scansions and troughs occuring at the middle of each of said field scansions; and proportioning network means including a parallel arrangement of a resistor and a capacitor connected in series between the cathode circuit of said electron tube and said convergence wave form generating circuits, said resistor and capacitor being proportioned relative to one another and to said biasing network to bias said electron tube for proper operation of said deflection system and to so relate the direct current and alternating current components of the parabolic current waves that, at the troughs of said waves, the respective currents through said electromagnet coils always have substantially the same magnitudes irrespective of the particular shapes and peak-to-peak amplitudes of said waves, whereby said convergence waveform generating circuits can be adjusted to provide dynamic beam convergence at the edges of the kinescope screen without materially changing the beam convergence at the center of the screen, and to suitably bias said electron tube for proper operation of said deflection system.

9. In a color television receiver including a multiplebeam color kinescope and provided with a deflection system for said beams, a beam convergence system comprising: a plurality of beam convergence electromagnets having energizing coils; a transformer in said deflection system and having a primary winding traversed by a substantially sawtooth current and a secondary winding inductively coupled to said primary winding and in which pulses are produced at said deflection frequency; means including two inductance coils coupled to said secondary winding to convert said pulses into a substantially sawtooth wave; means coupling a first one of said inductance coils to at least a first one of two of said electromagnet coils to convert said sawtooth wave into a substantially parabolic current through said first electromagnet coil; means coupling the second one of said inductance coils to the second one of said two electromagnet coils to convert said sawtooth wave into a substantially parabolic current through said second electromagnet coil; a sawtooth current coil inductively coupled to said second inductance coil and connected to a selected one of said two electromagnet coils to effect a substantially sawtooth current flow in said selected electromagnet coil; and means for varying the inductance of said second inductance coil without significantly affecting said sawtooth current coil.

10. In a color television receiver, a beam convergence system in accordance with claim 9 in which said selected electromagnet coil is said first one of said two electromagnet coils.

11. In a color television receiver including a three beam color kinescope and provided with a line frequency deflection system for said beams, a beam convergence system comprising: a plurality of beam converge electromagnets having respective energizing coils; an output transformer connected in said deflection system and hav ing a primary winding traversed by a substantially sawtooth current and a secondary winding inductively coupled to said primary winding and in which pulses are produced at said line frequency; means including two inductance coils coupled to said secondary winding to convert said pulses into a substantially sawtooth wave; means coupling one of said inductance coils to two of said electromagnet coils to effect a substantially parabolic current flow in said two electromagnet coils; a sawtooth current coil coupled to the other of said inductance coils and connected to said two electromagnet coils to effect a substantially sawtooth current flow in said two electromagnet coils; and means comprising a magnetic core for varying the inductance of said second inductance coil without effecting a significant change in the sawtooth fiow in said two electromagnet coils.

12. In a color television receiver including a threebeam color kinescope and provided with a line frequency deflection system for said beams, a beam convergence system comprising: three beam convergence electromagnets having respective energizing coils; an output transformer connected in said deflection system and hav ing a primary winding traversed by a substantially sawtooth current and a secondary winding inductively coupled to said primary winding and in which pulses are produced at said line frequency; means including two inductance coils coupled to said secondary winding to convert said pulses into a substantially sawtooth wave; means coupling a first one of said inductance coils to two of said electromagnet coils to convert said sawtooth wave into a substantially parabolic current through said two electromagnet coils; means coupling the second one of said inductance coils to the third one of said electromagnet coils to convert said sawtooth wave intoa substantially parabolic current through said third electromagnet coil; a sawtooth current coil inductively coupled to'said second inductance coil and connected to said two electromagnet coils to effect a substantially sawtooth current flow in said two electromagnet coils; and means comprising a movable magnetic core for varying the inductance of said second inductance coil to vary the amplitude of the parabolic current flow through said third electromagnet coil without effecting a significant change in the amplitude of the sawtooth current flow in said two electromagnet coils..

References (Iited in the file of this patent UNITED STATES PATENTS 1,880,362 Parmet Mar. 31, 1959 2,903,622 Schopp Sept. 8, 1959 2,987,647 Armstrong June 6, 1961 

1. IN A COLOR TELEVISION RECEIVER INCLUDING A COLOR KINESCOPE HAVING A SCREEN LUMINESCING IN DIFFERENT COLORS WHEN IMPINGED BY A PLURALITY OF ELECTRON BEAMS ADAPTED TO BE DEFLECTED TOGETHER OVER SAID SCREEN IN SUCCESSIVE TRACE SCANSION PERIODS AND ALTERNATING RETRACE SCANSION PERIODS, A BEAM CONVERGENCE SYSTEM COMPRISING: A PLURALITY OF BEAM CONVERGENCE ELECTROMAGNETS HAVING COILS WHICH EFFECT THE CONVERGENCE OF SAID BEAMS WHEN ENERGIZED BY RESPECTIVE PARABOLIC CURRENT WAVES EACH HAVING CRESTS OCCURRING DURING BEAM RETRACE SCANSION PERIODS AND TROUGHS OCCURRING SUBSTANTIALLY AT THE MIDDLE OF BEAM TRACE SCANSION PERIODS, AND EACH HAVING DIRECT CURRENT AND ALTERNATING CURRENT COMPONENTS RELATED TO ONE ANOTHER IN A PREDETERMINED RATION SUCH THAT, AT THE TROUGHS OF SAID PARABOLIC CURRENT WAVES, THE RESPECTIVE PARABOLIC WAVES ALWAYS HAVE THE SAME MAGNITUDES IRRESPECTIVE OF THE PARTICULAR SHAPES AND PEAK-TO-PEAK AMPLITUDES OF SAID PARABOLIC WAVES; A BEAM DEFLECTION SYSTEM TRAVERSED BY A SAWTOOTH CURRENT WAVE FOR EFFECTING SAID BEAM SCANSION OVER SAID SCREEN, SAID SAWTOOTH CURRENT WAVE HAVING DIRECT CURRENT AND ALTERNATING CURRENT COMPONENTS RELATED TO ONE ANOTHER IN A RATIO GREATER THAN SAID PREDETERMINED PARABOLIC CURRENT WAVE RATIO; TWO CURRENT DIVIDING CIRCUITS INCLUDING RESPECTIVE IMPEDANCE MEANS AND CONNECTED TO SAID DEFLECTION SYSTEM FOR TRAVERSAL BY RESPECTIVE PORTIONS OF SAID SAWTOOTH CURRENT WAVE, THE IMPEDANCE MEANS OF ONE OF SAID CIRCUITS COMPRISING A RESISTOR-CAPACITOR NETWORK, SAID RESPECTIVE IMPEDANCE MEANS HAVING SUCH VALUES AS TO ENABLE PROPER OPERATION OF SAID BEAM DEFLECION SYSTEM AND BEING PROPORTIONED RELATIVE TO ONE ANOTHER SUCH THAT THE SAWTOOTH CURRENT WAVE TRAVERSING SAID ONE CURRENT DIVIDING CIRCUIT HAS SAID PREDETERMINED RATIO OF DIRECT CURRENT AND ALTERNATING CURRENT COMPONENTS; AND MEANS CONNECTING SAID ONE CURRENT DIVIDING CIRCUIT TO SAID ELECTROMAGNET COILS TO CAUSE THE TRAVERSAL OF SAID COILS BY RESPECTIVE PARABOLIC CURRENT WAVES HAVING SAID PREDETERMINED RATIO OF DIRECT CURRENT AND ALTERNATING CURRENT COMPONENTS, WHEREBY SAID BEAM CONVERGENCE SYSTEM CAN BE ADJUSTED TO PROVIDE DYNAMIC BEAM CONVERGENCE AT THE EDGES OF THE KINESCOPE SCREEN WITHOUT MATERIALLY CHANGING THE BEAM CONVERGENCE AT THE CENTER OF THE SCREEN. 